The spectrum of infectious diseases contributing to pediatric morbidity and mortality has evolved considerably over the last century. Infections such as diphtheria, peri:ussis, and tetanus, now largely unseen even in developing areas of the world, were major killers before the advent of antibiotics and vaccines. Effective and widespread prevention and treatment of bacterial pathogens primarily affecting infants and children, such as Streptococcus pneumoniae and Hemophilus influenzae, have resulted in the recognition of viral infections as prominent causes of pediatric morbidity and mortality. The role of viral pathogens is exacerbated by advances in immunosuppressive therapy for malignancies and autoimmune disorders, which render the host susceptible to relatively benign viral infections. Surprisingly, there is only a small armamentarium of antiviral agents and limited understanding of viral pathogenesis and host responses to viral pathogens, especially among children. In the developing world, few antiviral agents are available, established vaccines such as those directed against measles and hepatitis B are not widely available, and the HIV pandemic has resulted in >300,ooo HIV-infected children/year and 15 million orphans globally. There is a clear need to address the identification, treatment and prevention of viral infections in children. The purpose of this training grant is to provide rigorous preparation for trainees in pediatric infectious diseases to develop academic careers, in the domestic and international setting, with a focus on viral infections in children. One postdoctoral Pediatric Infectious Diseases trainee per year will be selected to participate in the three year training program, although support is only requested for the last two research years. Although not a degree-granting program, there is a required curriculum, and enrollment in courses offered in the Masters of Epidemiology program and the Department of Microbiology and Immunology at Stanford University is encouraged. The program is based on the success of the Stanford University Division of Pediatric Infectious Diseases since its inception in 1978 in producing nationally known scholars and researchers. It is structured to allow trainees to choose from basic science, translational, and epidemiological research tracks with mentors from the Departments of Medicine, Microbiology and Immunology, and Pathology, and with collaborators from the University of Zimbabwe, the University of California Berkeley School of Public Health, and the Universidad Autonoma and Hospital Infantil in Mexico City, v\dth the goal of studying pathogenesis and host response to viral pathogens in children. RELEVANCE (See instructions): This grant will train Pediatric Infectious Diseases fellows to become domestic and international academic researchers vsdth a focus on identification, prevention and treatment of viral infections of children.